Is knob and tube wiring illegal in Ontario?

No. Existing knob and tube is not prohibited and does not have to be removed by code in itself. What ends its life is insurance — many underwriters will not write or renew a policy on a house with active knob and tube, and a mortgage lender may follow. It is a commercial problem with a technical cause, not the other way round.

Can aluminium wiring be fixed without a full rewire?

Usually. Insurers frequently accept properly remediated terminations — approved connectors at every device, junction and panel lug, done throughout — instead of replacement, and it costs a fraction of a rewire. Whether yours accepts it differs between insurers, so ask before booking anything.

What makes knob and tube genuinely dangerous rather than merely uninsurable?

Two situations. Wiring buried in attic insulation, because the system relies on open air to shed heat and insulation removes that. And a circuit that has been extended with modern cable spliced into it outside a box, which is common in houses that have been partly updated. Neither is visible from the ground floor.

How much does a whole-house rewire cost?

Published 2026 Ontario guidance puts a full rewire at $8,000 to $20,000 or more, depending on size, access and how much of the finished surface has to come off. Aluminium remediation is far less. A staged rewire — service and panel first, heavy circuits next, the rest after — spreads it, provided the notification of work covers the whole scope so the eventual inspection signs off one job rather than three partial ones.

How do I know which one I have?

Knob and tube is pre-1950: separate conductors running through porcelain knobs and tubes, cloth insulation, and every outlet in the house is two-prong. Aluminium branch wiring is roughly 1965 to 1978 and is marked on the cable jacket; the giveaway at the panel is dull silver conductors rather than copper. A photograph of the panel with the door open usually settles it.

Knob and Tube and Aluminium: What Insurers Actually Want

Two wiring systems get Ontario houses declined at renewal, and they come from opposite ends of the last century.

Knob and tube is pre-1950. Aluminium branch wiring is roughly 1965 to 1978. Neither is unsafe in the abstract. Both are treated as unsafe by underwriters — which, if you are the one holding the policy, amounts to precisely the same thing.

The good news, before any of the bad: one of these two has an accepted middle path that costs a fraction of a rewire. The other does not, and no amount of shopping around changes that.

Around here the first is concentrated in the pre-war town cores — the shipyard grid in Collingwood, the streets climbing away from the harbour in Midland, the blocks between the lakes in Orillia, the heritage main street in Creemore. The second is spread evenly across everything built in the two decades after that.

Knob and tube

It is an open-air system. The conductors run separately through porcelain knobs and ceramic tubes, and they rely on the air around them to shed heat.

Which works beautifully right up until somebody insulates the attic. Then the wiring is buried in the one thing it was designed not to be buried in. A great deal of pre-war housing around here has been insulated once or twice since — usually for an energy rebate, decades after the wiring went in, and without anybody connecting the two decisions.

It also has no equipment grounding conductor. That is why every outlet in a knob-and-tube house has two prongs, and why the three-prong adaptors people fit are genuinely worse than the problem they solve: they present a grounded receptacle to an appliance that has nothing grounded behind it.

There is no accepted middle path

This is the important difference from aluminium, and we would rather say it plainly than let you find out after paying somebody for a half-measure. No connector, no treatment and no partial measure makes knob and tube acceptable to an underwriter while leaving it in place. The circuits get replaced.

What can be staged is the order. The usual sequence is service and panel first, then the circuits carrying the heaviest load, then the remainder — with a single notification of work filed with the Electrical Safety Authority covering the whole scope, so the eventual inspection signs off one finished job rather than three partial ones.

The partly-updated house is the hard case

The most common finding in Midland and Penetanguishene is not an untouched knob-and-tube house at all. It is a house where the ground floor was rewired at some point, the upper floor was not, and the join sits somewhere nobody wrote down.

Untouched is easier to quote and easier to work on, oddly enough. Partly updated means opening finished surfaces just to find out where the modern cable stops — which is why those quotes carry a range rather than a number.

Aluminium branch wiring

Aluminium is a perfectly good conductor. The failure is entirely at the terminations.

It expands and contracts more than copper, so a connection worked by daily heating cycles loosens off. It creeps under a screw — slowly deforms, and the contact pressure drops away. And it oxidises into a resistive layer, where copper oxide stays reasonably conductive.

Every one of those concentrates heat at the connection rather than in the wire. Which is why aluminium problems turn up at outlets, switches and panel lugs, and effectively never in the middle of a run.

The middle path insurers do accept

Approved connectors at every device, every junction and every panel lug, throughout the house. Not a sample. Not just the visible ones.

It costs a fraction of replacement, and it is the whole reason aluminium is a far cheaper problem to have than knob and tube. Whether your insurer accepts it genuinely differs between insurers — so one phone call is worth more to you than any quote on this page.

What this costs

City Power’s 2026 Ontario guide puts a whole-house rewire at $8,000 to $20,000 or more. A useful rule of thumb from the same guide is $4,000 to $8,000 per 1,000 square feet, ESA notification on top. What moves a house inside the band is floor area, access, and how much finished surface has to come off. Balloon framing in a pre-war house gives a lovely clear vertical run from sill plate to attic, which helps a great deal. A 1960s bungalow full of fire stops does not.

Aluminium remediation is far less, and it scales with the number of devices rather than the size of the house.

Neither number includes the panel. If the service is 60 A — and in the pre-war stock it frequently is — the service upgrade is a separate job that usually goes first. A rewire terminating in a fuse panel solves about half the insurance problem, which is not a satisfying place to stop.

What we will tell you not to spend money on

If you have aluminium and your insurer accepts remediated terminations, do not buy a rewire. Ask the insurer first, in writing, and get that answer before anybody quotes you anything.

If you have a grounding conductor and two-prong receptacles, ground-fault protection with correct labelling is frequently a compliant answer. That is not a rewire, and it is not priced like one.

And if a home inspector wrote “recommend evaluation by a licensed electrical contractor” without saying which system they actually saw, pin that down before commissioning a thing. The two problems on this page differ by an order of magnitude in price, and the words in an inspection report do not reliably tell them apart.